1. Field of the Invention
The present invention relates to a semiconductor optical device and a method for manufacturing a semiconductor optical device.
2. Description of the Related Art
Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2011-039262) discloses a semiconductor optical modulator. Patent Literature 2 (U.S. Pat. No. 6,310,995) discloses a spot size converter (SSC).
Patent Literature 1 discloses a structure in which an electrical isolation groove is disposed in a semiconductor optical modulator. The isolation groove is formed by removing a portion of a cladding layer in the semiconductor optical modulator. At an end of the isolation groove, the cladding layer has a tapered portion. In the SSC disclosed in Patent Literature 2, two waveguides are stacked one on top of the other in a vertical direction. These waveguides have a two-stage mesa structure. The upper waveguide has a taper structure.